USRobotics V.34 user manual Figure H-3⎯Data Flow During Remote Digital Loopback

COURIER HIGH SPEED MODEMS

REMOTE DIGITAL LOOPBACK⎯&T6, &T7

This test, like the local digital loopback test, verifies the condition of both modems and the phone link. Data flow is shown in Figure H-3.

Figure H-3⎯Data Flow During Remote Digital Loopback

The request for and granting of Remote Digital Loopback testing requires that both modems use ITU-T V.22 standard signaling. The test must be performed at 2400 bps or lower. If the remote modem does not have the capability or is not set to respond (&T4), you will get an ERROR result code.

As with Analog Loopback, there are two Remote Digital Loopback options. If you select &T6, you send keyboard data to the modem and verify it when it is returned over the phone lines and to your screen. If you select &T7, the modem sends its internal test pattern and returns an error count to your screen.

NOTE: Both test options require the modem to establish a connection and return to online-command mode in response to the +++ escape code. DIP switch 9 must be set ON so that the modem does not hang up on receipt of the escape code. If necessary, set the switch ON and then issue the ATZ command to the modem to initiate the new switch setting.

&T6

1.Set the software to 2400 bps or lower. Set the modem to &M0. If you wish, set the S18 timer.

Establish a connection with the remote modem. If you haven't already done so, arrange with the remote user to cooperate with your testing and, if necessary, set the remote modem to acknowledge the RDL request. For example, older U.S. Robotics high speed modems need to be set to S16=8.

H-6 Modem Testing